Investigation of optical parameters of boron doped aluminium nitride films grown on diamond using spectroscopic ellipsometry

Boron doped aluminium nitride (B)AlN films are prepared on diamond substrate by using a co-sputtering system. The dielectric function of diamond substrate and (B)AlN films with B contents of 0%, 3%, 5% are extracted by using the spectroscopic ellipsometry. Whereas the (B)AlN films having B contents lower than 5% are considered important for improving crystalline and electronic properties of the buffer layers - the films with B contents <= 3%, however, do not cause appreciable changes in its direct bandgaps.